Coaxial bi-directional catheter

ABSTRACT

A deflectable catheter including an outer member having a proximal portion and a distal portion, an elongated column member extending distally from the outer member and an inner member positioned coaxial with the outer member and attached to the column member. The inner member extends distally of the outer member and has a distal tip portion. A reinforcement member is positioned over the column member to restrict axial movement of the column member such that when one of the inner member or outer member is moved with respect to the other, axial compression of the column member is restricted by the reinforcement member causing the distal tip portion of the inner member to deflect laterally.

This application is a divisional of application Ser. No. 14/064,170,filed Oct. 27, 2013, now U.S. Pat. No. 9,233,225, which claims priorityfrom provisional application Ser. No. 61/724,921, filed Nov. 10, 2012.The entire contents of each of these applications are incorporatedherein by reference.

BACKGROUND

Technical Field

This application relates to medical devices, and more particularly, tomedical catheters with steering capabilities for use in trackingtortuous pathways or deflecting and/or placing accessories.

Background of Related Art

The concept of a variable stiffness microcatheter for use in navigatinginto tortuous narrow vasculature for delivery of treatment options suchas fluid injection or coil placement is disclosed in U.S. Pat. No.4,739,786, to Engelson. This is achieved by steam shaping the variablestiffness catheter's distal tip and tracking the catheter in combinationwith a guidewire, straight or curved. While this method allows forquick, accurate access to remote areas such as those in the brain, itdoes not allow for slight distal tip adjustments to aid in treatmentonce the destination site is reached. If adjustments are needed, thecatheter or the guidewire, or in some instances both, would have to beremoved and re-shaped.

U.S. Pat. No. 6,726,700, to Levine, and U.S. Pat. No. 7,591,813, toLevine et al., attempted to correct this shortcoming by disclosing amicrocatheter with a deflectable distal tip. Levine describes aco-linear catheter comprising a flexible joint or hinge region defininga main lumen, used for delivery of guidewires and accessories, and awire lumen that contains a push/pull wire, which is secured to thedistal tip with a radiopaque band. Flexion, or bending, of the hingeregion is achieved through remote manipulation of the push/pull wire.While this design might work well on a laboratory bench top or instraight vasculature, it fails to consistently deflect in narrow,tortuous anatomy due to its co-linear design featuring the push/pullwire/hinge construction and the inability to introduce fluid into thewire lumen to act as a lubricant to aid in reducing friction between themovable push/pull wire and the wire lumen.

Both of the Levine patents disclose a co-linear, dual lumen (main lumenand wire lumen) deflectable catheter with tip deflection that is broughtabout through manipulation of a push/pull wire residing in the wirelumen which cannot be lubricated with fluid. Neither of the abovementioned devices disclose a coaxial (inner catheter and outer catheter)device that uses manipulation of the main lumen (inner catheter) andlubrication to bring about smooth, consistent deflection needed to aidin navigation along a small diameter tortuous pathway and to allow forslight tip adjustments to ensure accuracy in delivering fluids andaccessories upon arrival at the desired site, as disclosed herein.

SUMMARY

The present invention provides a coaxial bi-directional deflectablecatheter which overcomes the above discussed limitations in tipmanipulation in narrow, tortuous anatomy.

The present invention provides in one aspect a deflectable cathetercomprising an outer member having a proximal portion and a distalportion, an elongated column member extending distally from the outermember, and an inner member positioned coaxial with the outer member andattached to the column member. The inner member extends distally of theouter member and has a distal tip portion. A reinforcement member ispositioned over the column member to restrict axial movement of thecolumn member such that when one of the inner member or outer member ismoved with respect to the other, axial compression of the column memberis restricted by the reinforcement member causing the distal tip portionof the inner member to deflect laterally.

In some embodiments, the outer member has a central longitudinal axisand the column member is radially offset with respect to the centrallongitudinal axis of the outer member.

In some embodiments, the lateral reinforcement member comprises a tube.Preferably, in some embodiments, the tube is a helically wound flexiblecoil. In some embodiments, the column member is fixedly attached to theouter member and the inner member. In other embodiments, the columnmember is attached only to the inner member.

The outer member can have a central lumen to receive the inner memberand/or the inner member can have a central lumen to receive a guidewireor other accessory. The central lumen of outer member can be lubricatedto facilitate movement of the inner member therein to facilitate thedeflection.

The column member is preferably non-circular in cross section. In someembodiments, the column member has a proximal portion attached to thedistal portion of the outer member and a distal portion attached to thedistal portion of the inner member.

The catheter can further include a marker band at the distal portion ofthe inner member and the column can be attached to the marker band. Insome embodiments, a proximal portion of the column member terminates ata distal portion of the outer member.

Preferably, upon movement of the inner member proximally or the outermember distally, the axial compression of the column member is limitedby the reinforcement member so it cannot fail axially but instead failslaterally to deflect the distal tip portion.

In some embodiments the catheter includes first and second marker bandson the inner member, and the column member is attached to the first andsecond marker bands.

A locking assembly can be provided to lock the position of the innermember with respect to the outer member.

The inner member can have a cut tube at its distal end portion toprovide flexibility.

In accordance with another aspect of the present invention, the presentinvention provides a deflectable catheter comprising a proximal portion,an intermediate portion and a deflectable distal tip portion. A firstmovable member is axially movable from a first position to a secondposition, wherein the distal tip portion is deflectable by an axialmovement of the first member in which the distal tip portion cannot failaxially in compression so it fails laterally causing deflection of thedistal tip portion in a first direction.

In some embodiments, the first movable member is positioned within asecond member, and the first position is distal of the second position.In other embodiments, the first movable member is positioned over asecond movable member and the first position is proximal of the secondposition. In some embodiments, the first movable member deflects whilethe second movable member remains substantially stationary. In someembodiments, axial movement in an opposite direction causes a bending ofthe distal tip portion in the opposite direction.

The present invention provides in accordance with another aspect adeflectable catheter having a deflectable distal tip portion comprisingan outer catheter having a lumen, a proximal portion and a distalportion, an elongated member extending distally from the outer member,and an inner catheter positioned coaxially within the inner lumen of theouter catheter and attached to the elongated member, wherein axialmovement of one of the outer member and inner member causes the distaltip portion of the catheter to deflect laterally.

In some embodiments, the elongated member is attached to the innermember and is surrounded by a movement restriction member to restrictaxial movement of the column member when the outer member or innermember is moved axially relative to the other. Preferably, such axialrestriction limits axial compression of the column member upon axialmovement in one direction. In some embodiments, a tip of the innercatheter deflects and a tip of the outer catheter does not deflect.

Preferably, movement of the inner catheter in one direction causes axialcompression of the elongated member and movement of the inner catheterin a second direction causes bending of the elongated member to causedeflection in a second opposite direction.

In accordance with another aspect of the present invention, adeflectable catheter having a deflectable distal tip portion is providedcomprising an outer catheter having a lumen, a proximal portion and adistal portion, an inner catheter positioned coaxially within the innerlumen of the outer catheter and having a distal tip portion extendingdistally of a distal end of the outer catheter, and a column memberattached to the inner catheter, wherein axial movement of one of theouter member and inner member acts on the column member to cause thedistal tip portion of the inner catheter to deflect laterally.

In some embodiments, the column member includes a proximal stopcontacted by the outer catheter.

The present invention also provides in accordance with another aspect acoaxial bi-directional deflectable catheter which can be lubricatedinternally through external application to help overcome frictionbetween the inner catheter and the outer catheter while deflecting thedistal tip in narrow, tortuous vasculature. In a method for lubricatingthe deflection lumen formed by the inner diameter of the outer catheter,a syringe filled with fluid can be connected to a side arm. The side armcan be part of a locking assembly, and prior to the procedure, with thelocking assembly in a locked position, fluid is injected into the innerlumen of the outer catheter. The locking assembly can then be opened andthe inner catheter pulled and pushed to deflect the tip, with the fluidensuring smooth movement. With the locking assembly locked, the catheterand guidewire can then be inserted and tracked through the anatomy. If,at any point, deflection is impaired, additional lubrication fluid canbe introduced through the side arm using a syringe.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present disclosure are described hereinwith reference to the drawings wherein:

FIG. 1 is a side view of a deflectable catheter of one embodiment of thepresent invention;

FIG. 2 is a side view of one embodiment of an inner catheter of thedeflectable catheter of FIG. 1;

FIG. 2A is an enlarged view of the distal portion of the inner catheterof FIG. 2;

FIG. 3 illustrates an inner catheter in accordance with anotherembodiment of the present invention;

FIG. 4 illustrates an inner catheter of yet another embodiment of thepresent invention;

FIG. 5 illustrates an inner catheter of still another embodiment of thepresent invention;

FIG. 6 is a side view of one embodiment of the outer catheter of thedeflectable catheter of FIG. 1;

FIG. 7 is an enlarged view of the distal portion the outer catheter ofFIG. 6;

FIG. 8 is a side view of an outer catheter of another embodiment of thepresent invention;

FIG. 9 illustrates the inner catheter of FIG. 2 positioned inside theouter catheter of FIG. 6 to form the deflectable catheter;

FIG. 10 is an enlarged view of the distal portion of the catheter ofFIG. 9 with the lateral reinforcement (support) tube removed to show thecolumn;

FIG. 11 is an enlarged view of the distal portion of the deflectablecatheter of FIG. 10 with the lateral reinforcement tube;

FIG. 12A is a side view of the internal structure of the inner catheterof FIG. 5 showing the effect on the column of axial movement of theinner catheter in the proximal direction in the absence of the lateralsupport tube;

FIG. 12B is an enlarged view of the internal structure of the innercatheter of FIG. 5 showing the effect on the column of axial movement ofthe inner catheter in the distal direction in the absence of the lateralsupport tube;

FIG. 13A is an enlarged view showing the effect of axial movement of theinner catheter in the proximal direction in the presence of the lateralsupport tube;

FIG. 13B is an enlarged view showing the effect of axial movement of theinner catheter in the distal direction in the presence of the lateralsupport tube;

FIG. 13C is a side partial cutaway view illustrating movement of thecolumn as in FIG. 13A;

FIG. 13D is a side partial cutaway view illustrating movement of thecolumn as in FIG. 13B;

FIG. 14 is an enlarged cross-sectional view of a rotation control memberfor controlling rotation between the inner catheter and the outercatheter in accordance with an embodiment of the present invention;

FIG. 15 is a side view of a proximal portion of an alternate embodimentof the deflectable catheter having a locking assembly with a side armfor fluid introduction;

FIG. 16 is a side view of an alternate embodiment of a locking assemblyfor manipulating and locking the distal deflecting tip of the catheter;

FIG. 17 is a side view of an alternate embodiment of the deflectablecatheter of the present invention having a rapid exchange port;

FIG. 18A is a side view of another alternate embodiment of the mechanismfor deflecting the distal tip of the catheter with the lateralreinforcement tube removed for clarity;

FIG. 18B illustrates the mechanism for deflecting the distal tip ofcatheter of FIG. 18A with the lateral reinforcement tube shown; and

FIGS. 19A and 19B are side views of a distal portion of alternateembodiments of the deflectable catheter of the present invention havinga balloon.

DETAILED DESCRIPTION

The present application provides a bi-directional deflectable catheterwith enhanced deflection to enable and facilitate tip deflection innarrow tortuous vasculature. Various embodiments of the deflectablecatheter are disclosed herein which include various embodiments of boththe inner catheter (inner member) and the outer catheter (outer member)which make up the structure of the microcatheter. The catheter has adeflectable distal tip portion which is deflected due to the arrangementof the inner catheter, outer catheter and column member which isattached to the inner catheter. The column member has a movementrestriction member thereover. Relative movement of the outer catheterand inner catheter effects lateral deflection of the distal tip portiondue to the restriction member limiting lateral movement of the column.This is explained in more detail below. The structural elements of thecatheter and variations thereof will first be described.

Turning to a first embodiment and with reference to FIG. 1 abi-directional coaxial deflectable microcatheter is illustrated anddesignated generally by reference numeral 10. The catheter 10 includesan inner catheter (member) 12, an outer catheter (member) 24 and adistal portion 48 with a deflectable tip.

The inner catheter 12, which extends through a lumen in outer catheter24, is composed of a catheter body that is constructed of a thin walledbody or tube 14 that extends between proximal end 16 and distal end 58having an inner lumen with a diameter in the range of about 0.001″inches to about 1.993″ inches with a preferred inner diameter of about0.017″ inches. Coupled to the proximal end of inner catheter body 14 iswinged hub 20, which sits on a strain relief 22 which optionally can beprovided. The winged hub (luer) 20 can be made of plastic. If desired,winged hub 20 can also be fitted with a rotating hemostatic valve (RHV)18 to provide a channel into the inner lumen of inner catheter 12 forinsertion of an accessory or fluid introduction through the side arm.Possible accessories may include by way of example: guidewires, coils,fiberscopes, forceps, video cameras, laser or electrohydrauliclithotripsy devices, and illumination or laser fibers. Other accessoriescan also be inserted through the channel.

Outer catheter 24 is composed of a catheter body that is constructed ofa thin walled body or tube 26 having an inner lumen that extends betweenproximal end 28 and distal end 44 having an inner lumen with a diameterin the range of about 0.007″ to about 1.999″ with a preferred innerdiameter of about 0.027″. Outer catheter body 26 also features arelatively stiff proximal section 40 that is joined to a relativelyflexible distal section 42. Coupled to the proximal end of outercatheter body 26 is winged hub (luer) 34, which sits on strain relief 38which optionally can be provided. Attached to winged hub 20 is rotatinghemostatic valve (RHV) 32 with end cap 30 and side arm 31. End (lock)cap 30 acts as the locking assembly for the deflectable catheter whileside arm 31 is used for introduction of fluids for lubrication andpossibly visualization. The lubrication can facilitate relative movementof inner catheter 12 during the procedure which facilitates deflectionby ensuring smoother relative movement of the inner and outer catheters.When cap 30 is fully opened, inner catheter 12 is free to move axiallyresulting in distal tip 48 deflection as described below. Cap 30 can betightened at any point in the deflection process to clamp and hold innercatheter 12 in position and thereby lock the tip 48 in place.

Deflectable tip 48 of inner catheter 12 is covered with lateral supporttube 50, which overlies the column member described below. Support tube50 is adhered at its proximal and distal ends 46 and 52, respectively,as shown in FIG. 11 and described below. Preferably lateral support tube50 is a helically wound flexible coil with an outside diameter in therange of about 0.008″ to about 2.00″ with a preferred diameter of about0.034″. The coil may be made from a polymer or metal material but thepreferred material is platinum/iridium for radiopacity. Disposeddistally of lateral support tube 50 is marker band 54, which is adheredat end 56 to the distalmost end 58 of the inner catheter 10. The band 54can be made from a polymer or metal, the preferred material isplatinum/iridium for radiopacity.

FIGS. 2 and 2A illustrate one embodiment of inner catheter 12 ofdeflectable catheter 10. The inner catheter 12 as discussed aboveincludes a winged hub 20, which sits on an optional strain relief 22 andoptional RHV 18. Inner catheter 12 also includes catheter body 14 whichpreferably has a stiff proximal section 60 made up of a braid reinforcedpolymer tube that has an outer diameter in the range of about 0.002″ toabout 1.994″ with a preferred diameter of about 0.023″ and a length thatextends between proximal end 16 and distal end 62 in the range of about0.5 inches to about 34 feet with a preferred length around 110 cm.Proximal section 60 is coupled at a distal end to a less stiff distaltube 64 that can be made of a braid or coil reinforced polymer but ispreferably made up of high density polyethylene (HDPE) that has an outerdiameter in the range of about 0.002″ to about 1.994″ with a preferreddiameter of about 0.022″ and length that extends from a proximal end(adjacent distal end 62 of proximal section 60) to distal end 68 in therange of about 0.5 inches to about 34 feet with a preferred lengtharound 45 cm. The overall usable length for the combined proximal anddistal sections has a range of about 0.5 inches to about 34 feet with acontinuous inner diameter in the range of about 0.001″ to about 1.993″with a preferred useable length being approximately 150 cm and with apreferred inner diameter of about 0.017″. Inner catheter body 14 furtherincludes laser cut tube 76, with window 74, which is coupled to distaltube 64 at its distal end 70. Laser cut tube 76 can be made of plasticor metal but is preferably made of super elastic nitinol with an innerdiameter in the range of about 0.001″ to about 1.993″ with a preferreddiameter of about 0.017″. The outer diameter for laser cut tube 76 canrange from about 0.002″ to about 1.994″ with a preferred outer diameterof about 0.022″. The length of the laser cut tube can range from about0.5 inches to about 34 feet with a preferred length of approximately 1cm.

Distal portion 66 of inner catheter body 14 includes laser cut tube 76that is coupled to distal tube 64 using a tube 78, which is preferably apolyimide tube coated with adhesive 72. Preferably polyimide tube 78 hasan inner diameter in the range of about 0.001″ to about 1.993″ with apreferred inner diameter of about 0.0165″. The outer diameter ofpolyimide tube 78 can range from about 0.002″ to about 1.994″ with apreferred diameter of about 0.0175″. Preferably, the length of polyimidetube 78 can range between about 0.25 mm and about 1 cm with a preferredlength of approximately 3 mm.

The overall useable length of the inner catheter 12, which ranges fromabout 0.5 inches to about 34 feet, need not have separate materials forall of the sections (proximal, distal, and laser cut tube) describedabove. For instance, a laser cut nitinol tube (or other metal or plasticmaterial such as polyimide) can have the necessary stiffness variationsfor the proximal and distal sections designed into it resulting in asuitable inner catheter body that meets the ranges for inner catheter14.

FIG. 3 illustrates an alternate embodiment of the inner catheterdesignated by reference numeral 312. In this embodiment, the innercatheter body 314 has a lubricious inner liner 82 that runs fromproximal end 316 to distal end 358. The purpose of the liner is to helpreduce the coefficient of friction to aid in guidewire movement withinthe inner catheter 314. The liner can be made of materials such aspolytetrafluoroethylene (PTFE) or fluorinated ethylene propylene (FEP).

The liner 82 is topped with a combination of a continuous braid 84, coil102, and laser cut tube 106 to help with lumen integrity (reinforcement)and to aid in stiffness variation. The braid 84, which can be made offlat or round wire or a combination, runs from proximal end 316 todistal end 398. The braid can be made of materials such as stainlesssteel, nitinol, polymer, fiber or even a combination of materials. Thecoil 102, which can be made of flat or round wire, runs from proximalend 398 to distal end 104. The coil 102 can be made of materials such asstainless steel, nitinol, platinum/iridium or even a polymer. The lasercut tube 106 runs from proximal end 104 just about to distal end 358.Laser cut tube 106 can be nitinol or other metal or it can be cut frompolyimide as done by MicroLumen (Oldsmar, Fla.) or another polymer.

The reinforcement layer is topped with polymers with varying stiffnessesto create three distinct sections: proximal section 86, mid section 90,and distal section 96. Proximal section 86 extends distally fromproximal end 316 to distal end 362. Mid section 90 extends distally fromend 362 to distal end 94. Distal section 96 extends from end 94 todistal end 358. The stiffness will decrease from proximal section 86 todistal section 96. Reduction in stiffness can be achieved by usingdecreasing durometers of material from proximal to distal. Preferably,proximal section 86 can be formed using material 88 which can be a nylonor pebax having a durometer in the range of 60D to 75D or any othermaterial having a relative durometer hardness value of around 72D, midsection 90 can be formed using a lower hardness material 92 with adurometer of around 63D, and distal section 96 can be formed with aneven lower hardness material 100 such as a pellethane material having adurometer of 25D to 55D or other material having a durometer between 25Dand 40D. These are just examples of materials and durometers that can beused. Also, each section does not need to be formed with a single layerof material, if desired, sections can be constructed of two or morelayers. Actual material selection will be based on design needs forflexibility and stiffness. Additional layers of coils or braids may alsobe added as needed.

These layers are then fused together using a re-flow process (heat).Strain relief 322 and winged hub 320 are then added. Lastly, the innercatheter may optionally be coated on its outer diameter for a lengthwith a hydrophilic coating 108. The purpose of the coating is to aid inaxial movement of the inner catheter relative to the outer catheterduring the deflection process. If the coating requires hydration, liquidcan be injected through the side arm 31 on RHV 32 attached to outercatheter 10 (see FIG. 1).

As stated above, the typical microcatheter is formed using a re-flowtechnique which fuses all of the layers together with heat and, ifnecessary removable heat shrink tubing. As the length of the innercatheter (or outer catheter) increases to greater than 180 cm this maybe a problem due to current equipment restrictions. An alternate methodis to use non-removable heat shrink tubing of varying stiffnesses tocreate the proximal, mid, and distal sections. Also, although FIG. 3shows the braid 84, coil 102, and laser cut tube 106 stopping orstarting in either the proximal, mid, or distal section, each of thosecomponents can be made longer or shorter and as a result end or start atpoints different than shown.

FIG. 4 illustrates another embodiment of the inner catheter designatedgenerally by reference number 312. Construction of inner catheter body314′ is much the same as that of FIG. 3 with the exception of a longer,continuous coil 102′ for the laser cut tube 106. A marker band 110 isprovided. The marker band 110 may be made of platinum/iridium to aid invisualization under fluoroscopy or of other metals or plastics. The band110 can also be made from a coil rather than a solid tube as shown oreven omitted from the design. The remaining structure of the catheter isthe same as in FIG. 3 and therefore identical reference numerals areused to identify identical parts.

Another embodiment of the inner catheter is shown in FIG. 5. In thisembodiment, the inner catheter body 412 is made from a single stainlesssteel or nitinol hypotube (or alternatively a plastic or polyimide) thathas a laser cut spiral section 116 that extends from proximal end 114(adjacent distal section 415) to distal end 458. If needed, the proximalend of the inner catheter body 414 can have texturing, such as axialknurling, contouring, or even additional layers or perpendicularfeatures added to aid in pushing/pulling and locking. The catheter 412includes strain relief 422 and winged hub 420 at proximal 416. As inother embodiments, an optional outer shrink tubing or polymer layerand/or an inner lubricious layer can be added to the embodiment of FIG.5 to restrict stretching or misalignment of the spiral coil due to axialmovement and bending.

Turning now to the outer catheter structure of the microcatheter, andwith initial reference to FIG. 6, this Figure illustrates one embodimentof outer catheter 24 of deflectable catheter 10. In this embodiment, asnoted above, outer catheter body 26 has RHV 32 with locking cap 30 andside arm 31 attached to winged hub 34. Winged hub 34 sits on strainrelief 38, both of which are coupled to catheter body 26.

Outer catheter body 26 has a lubricious liner 128 that runs fromproximal end 28 to distal end 44 and has an inner diameter with a rangeof about 0.007″ to about 1.999″ and a preferred inner diameter ofapproximately 0.27″. The purpose of the liner 128 to is aid in movementof the inner catheter during the deflection process by reducing thecoefficient of friction between the outer catheter inner diameter andthe inner catheter outer diameter. The liner can be made of materialssuch as polytetrafluoroethylene (PTFE) or fluorinated ethylene propylene(FEP).

The liner 128 is topped with a reinforcement layer of a continuous openpitch coil 130 that runs from proximal end 28 to distal end 44. The coil130 can be made of flat or round wire. The coil 130 can be made ofmaterials such as stainless steel, nitinol, platinum/iridium or even apolymer or fiber. Also, the coil 130 need not be open pitch or acontinuous length for the entire length of outer catheter body 26. Forinstance, the distal end may need to have a certain length ofradiopacity and therefore require a platinum/iridium coil. To keep costlow, only the section requiring radiopacity could be platinum/iridiumwhile the remainder of the body could be covered with a lower cost coil,such as a stainless steel version.

The reinforcement layer is topped with polymers with varying stiffnessesto create three distinct sections: proximal section 118, mid section120, and distal section 122. Proximal section 118 extends distally fromproximal end 28 to distal end 124. Mid section 120 extends distally fromdistal end 124 of proximal section 118 to distal end 126. Distal section122 extends from distal end 126 of mid section 120 to distal end 44. Thestiffness will decrease from proximal section 118 to distal section 122.Reduction in stiffness can be achieved by using decreasing durometers ofmaterial from proximal to distal. For instance, proximal section 118 canbe formed using material 132 which can be a nylon or pebax having adurometer in the range of 60D to 75D or any other material having arelative durometer hardness value of around 72D, mid section 120 can beformed using a lower durometer material 134 with a durometer of around63D, and distal section 122 can be formed with an even lower hardnessmaterial 136 such as a pellethane material having a durometer of 25D to55D or other material having a durometer between 25D and 40D. These arejust examples of durometers that can be used, as actual materialselection can be modified to optimize the balance of flexibility andstiffness. The layers that are selected are then fused together usingheat. Alternatively, the entire outer catheter body can be made of asingle durometer tube from materials such as HDPE, LDPE, nylon polyimideor polyurethane. A lubricious liner and reinforcement coil or braid mayoptionally be added to this tube as well. If needed, one or more lumens(for delivery or balloon inflation) can then be added in parallel alongthe length of outer catheter body 26 using adhesive or one or more heatshrink tubings, which may or may not be removed and may have differingdurometers. The winged hub 34, strain relief 38, and RHV 32 with lockingcap 30 and side arm 31 are then added.

The final useable length for outer catheter 26 can range from about 0.5inches to about 34 feet with a preferable useable length of about 135cm. The proximal outer diameter can range from about 0.008″ (0.61 Fr) toabout 2.00″ (152 Fr) with a preferred proximal outer diameter of about 1mm (3 Fr) and a preferred distal outer diameter of about 0.93 mm (2.8Fr).

Outer catheter body 26 further includes a marker band 138, which isinserted mid way into the inner diameter at the distal end of outercatheter body 26. Preferably marker band 138 has a length in the rangeof about 0.005″ to about 1″ with a preferred length of about 0.039″ andan inner diameter in the range of about 0.0065″ to about 1.9985″ with apreferred inner diameter of about 0.0265″. The outer diameter has arange from about 0.0075″ to about 1.9995″ with a preferred outerdiameter of about 0.0285″. The marker band 138 can be made of a metal ora polymer tube or coil with a preferred material of platinum/iridium.

The catheter 10 includes an elongated longitudinally extending columnmember, e.g., a wire or tube, which extends distally of the outercatheter 24, and shown in FIG. 13C as a separate component, is attachedto the inner catheter, axially aligned at its ends, and is surrounded bya restriction (support) tube to restrict lateral movement of the columnmember. In one embodiment the column member includes a column 140, whichat its proximal end sits on marker band 138 or alternatively in a slotcut along the length of the marker band 138. The proximal portion ofcolumn 140 is also inserted into the inner diameter, i.e., the catheterbody wall, at the distal end of outer catheter body 26. Adhesive 146 isthen added to secure the parts in place. Preferably column 140 has asubstantially rectangular cross section with a thickness in the range ofabout 0.0005″ to about 0.5″ with a preferred thickness of approximatelyabout 0.002″. The width can range from about 0.0005″ to about 1.95″ witha preferred width of approximately about 0.005″. The column can have alength that ranges from 0.25 mm to 10 cm with a preferred length ofapproximately 8 mm. The column's preferred cross section is rectangularhowever other shapes such as oval can be used. A non-circular crosssection is preferred to effect bending in a desired direction. In apreferred embodiment, the column is in the form of a substantiallyrectangular wire or flat ribbon to control the plane of deflection.Also, cuts or other features can be added to the column to influencemovement. For example, the spacing and/or number of the cuts will effectmovement as it will affect flexibility. The thickness of the walls andthe dimensions will also affect flexibility and movement. The column canbe made of any metal or metal alloy and even a plastic, however thepreferred material is super elastic nitinol. Note the column 140 extendsdistally from the outer catheter distal end.

Distal portion 142 of outer catheter 24 includes distal end 44 havingflare 144 (FIG. 7) so that marker band 138 can be inserted approximatelymidway into outer catheter body 24 leaving a partial length exposed tocreate lip 148. Column 140 is then inserted in between lubricious liner128 and marker band 138 (which may or may not have a slot to accommodatethe column) until its proximal end is approximately flush with theproximal end of marker band 138. Adhesive 146 is then applied to joinall of the parts.

As an alternative to column 140 and marker band 138 being inserted astwo separate parts, the two can be made out of a single nitinol tube(laser cut) if desired or attached as a sub-assembly and then inserted.The band and column assembly may also be added during outer tubemanufacture in which case marker band 138 would be slid over alubricious liner.

An alternate embodiment of the outer catheter of deflectable catheter 10is illustrated in FIG. 8 and designated by reference numeral 524. Inthis embodiment, the coil 130 has been replaced by a proximal hypotube550 with a spiral cut that is butted or attached to the distal braid552. Lengths for the parts may vary depending on required flexibilityand stiffness needed for the part. The spiral cut hypotube 550 can bemanufactured from stainless steel, nitinol, polymers or a combination.Likewise, the braid can also be manufactured from stainless steel,nitinol, a polymer, fiber or a combination. The remaining components ofcatheter 524 are identical to catheter 24 of FIG. 6 and are thereforelabeled with the same reference numerals.

By comparing FIGS. 2 through 8 it can be seen that the inner catheterbody 14 and outer catheter body 526 can if desired be manufactured usingthe same materials and methods. Therefore, with the exception of lengthsand diameters, it is possible that both structures can be built using asingular design or a mix of the designs presented.

FIG. 9 illustrates inner catheter 12 and outer catheter 24, with column140 attached, aligned at distal portion 150. In manufacture, innercatheter 12 is inserted into outer catheter 24 until distal end 58 oflaser cut tube 76 is flush with the distal end of the column 140. Thelaser cut tube 76 is then rotated until connectors or ribs 80 are about90 degrees out of phase with the column 140 (and in a transverse planeand not underneath the column 140) to effect deflection in the desiredplane. The distal end alignment can be done before or after rotation fororientation.

Inner catheter 12 and outer catheter 24 are aligned and joined togetherwith marker band 54 and adhesive or solder joint 56 at distal portion150 (see FIG. 10). Preferably marker band 54 has a length in the rangeof about 0.005″ to about 1″ with a preferred length of about 0.039″ andan inner diameter in the range of about 0.0065″ to about 1.9985″ with apreferred inner diameter of about 0.0265″. The outer diameter has arange from about 0.0075″ to about 1.9995″ with a preferred outerdiameter of about 0.0285″. The marker band can be made of a metal or apolymer tube or coil with a preferred material of platinum/iridium. Asone alternate construction, lip 148, column 140, and marker band 54 canall be made out of a single laser cut part made of nitinol, stainlesssteel or other suitable material. As another alternate construction,column 140 can be soldered to marker band 138 and marker band 54 as asub-assembly. In another alternate construction, column 140 and lasercut tube 76 can be joined together at the distal ends using a jointformed from solder, glue, laser (depending on material), or otherjoining process not requiring a band.

The preferred embodiment for alignment of the distal ends of column 140and the inner catheter 12 (distal ends are approximately flush) is shownin FIG. 10. As an alternative, outer catheter 24 with column 140attached can be pulled back proximally along inner catheter 12 leaving aportion of the inner catheter body 14 exposed (without column coverage).Marker band 54 can then be slid over the distal end of catheter body 14,i.e., the tube 80, and then over column 140 until its distal edge alignswith the distal end of column 140. Joint 56 can then be formed. This setup will allow the bend radius of the device to remain at approximatelyhalf the column length while decreasing the crossing profile of thecatheter distal tip to the inner catheter's outer distal tip diameter.Note adjustments may have to be made to the distal tubing 80 (i.e., thelaser cut tube) for flexibility and coverage.

FIG. 11 illustrates distal portion 150 with lateral support tube 50 inplace which forms a cover for the column to provide the deflectionmethod and system of the microcatheter. Preferably, lateral support tube50 sits on lip 148 and is a closed pitch helically wound flexible coilmade of platinum/iridium with an outer diameter that ranges from about0.008″ to about 2.00″ with a preferred outer diameter of about 0.034″and an inner diameter that ranges from about 0.007″ to about 1.999″ witha preferred inner diameter of approximately about 0.030″. The preferredlength can range from about 1 mm to about 12 cm with a preferred lengthof approximately 6.5 mm. The coil may be made of any metal or plasticand may also be open pitched or a combination of open and closed pitchand optionally coated in plastic to form a solid flexible reinforcedtube. The lateral tube support (cover) 50 can also be made of a solidtube, that may or may not be laser cut, from plastic materials such asHDPE, LDPE, CFlex, latex, silicone, pebax, nylon, polyurethane orpolyisoprene. If solid tubes are used, drainage holes can be introducedon the lateral support tube or even outer catheter body to allow fluidintroduced through side arm 31 to exit. The distal portion 150 furtherincludes two joints 46 and 52 that adhere lateral support tube 50 inplace. As alternate options, lateral support tube 50 can be made tocover marker band 54 at its distal end or to extend past lip 148 on itsproximal end so that it sits directly on outer body 26 of outer catheter24 or the lateral support tube 50 can be laser cut into the distal endof the outer body 26.

The addition of the lateral support tube 50 and its joints completes thedeflectable catheter assembly. At this point, the outer diameter of thecatheter can be hydrophilically coated or, if needed, additional lumens(as discussed earlier) for accessories, such as video cameras, fibersoptics, or inflatable balloons can be added to the outer shaft. This maybe accomplished with adhesives and/or shrink tubing of varyingdurometers. If attachments are made, the hydrophilic coating would beapplied as the final step.

FIG. 12A illustrates distal portion 150 with spiral cut tip 156 (similarto the spiral cut tube of FIG. 5) on the end of inner catheter 12 underan axial pull load in the absence of the lateral support tube 50. Wheninner catheter body 14 is pulled axially by load 154 in the proximaldirection, the internal structure will want to shorten causing column140 to compress. FIG. 12B illustrates the effect when the inner catheterbody is pushed axially by load 155 in the distal direction in theabsence of lateral support tube 50. As shown, this applies a moment tothe end of the column causing it to bend. Note the load 154 (or 155)required to cause column 140 to move can be increased or decreased bychanging the dimensions e.g., cross sectional dimension of column 140.For instance, a stiff column formed for example by a larger crosssectional dimension will require more force to deform and therefore moreforce to deflect which can in certain instances be more advantageoussuch as providing more stability to the bent tip.

FIGS. 13A and 13C illustrate distal deflectable tip 48 under axial pullload 154 when lateral reinforcement (support) tube 50 is provided. Withlateral support tube 50 in place and axial pull load 154 applied, column140 can no longer axially compress due to the reinforcement of thecolumn by tube 50. As a result, the entire distal tip, including main(guidewire) lumen, deflects. Note as column 140 cannot be compressed andthe tip deflects it moves against the wall. As noted above, by varyingthe dimensions (or materials or cuts) of the underlying column 140, theload 154 to deflect the distal tip can be increased or decreased.However, if the column becomes too thin, the column will become unstableleading to multiple buckling points under load. This will result inlittle to no tip deflection.

FIGS. 13B and 13D illustrate the effect when the inner catheter body ismoved axially by load 155 in the distal direction when lateral supporttube 50 is provided. As shown, this bends the distal tip as in FIG. 12B.Note column 140 moves against the wall of the tube 50.

Note the movement discussed above and shown in FIGS. 12A-13D is movementof the inner catheter, proximally or distally, respectively, as shown.The same effect is achieved by movement distally or proximally,respectively, of the outer catheter. Movement of both the inner andouter catheters in the desired directions is also contemplated.

A rotation control member 158 for minimizing rotation between the innercatheter 12 and outer catheter 24 can be provided as shown in FIG. 14.Rotation control member 158 is fixedly attached to inner catheter body14 with joint 170. Flat section 168 on rotation control member 158 workswith flat section 166, which is formed by indentation 164 on outercatheter body 26, to control rotation or torquing of the cathetersrelative to one another. Rotation control member 158 further includesproximal lip 160, which acts as an axial stop when it comes in contactwith shoulder 162 on indentation 164. Rotation control member 158 ispreferably made of stainless steel but any metal or plastic can be used.The length can have a range from about 1″ to about 24 feet with apreferable length around 100 cm. Multiple short rotation members canalso be used and placed at various points along the outer diameter ofinner catheter body 14. Flat section 166 can also be formed directly ona hypotube, which can double as the proximal shaft for inner catheterbody 14.

The microcatheter can include a locking assembly 172 for manipulatingand locking the distal deflecting tip as shown in FIG. 15. Engagement ofbutton 174 allows the inner catheter 12 to be pulled or pushed axiallyrelative to the outer catheter 24 resulting in deflection of the distaltip. Once a deflected shape is decided upon, the button is released toset the shape. The button can also be held in (locked) so that the tipcan be reshaped freely with catheter advancement. Alternately, the outercatheter 24 can be moved relative to the inner catheter 12 while thebutton is engaged also bringing about deflection. If lubrication isneeded between the inner catheter and outer catheter to assist movementof the inner catheter, fluids such as saline or contrast can be injectedthrough side arm 176 of locking assembly 172. If no lubricant is needed,side arm 176 can be excluded from the design.

An alternate locking assembly for microcatheter 178 is illustrated inFIG. 16. Locking assembly 172 is designed for manipulating and lockingthe distal deflecting tip and has a rotational control system 180 builtin. Rotational control system 180 includes a stainless steel hypotube182 which overlies the inner catheter body and which has been flattenedin a region to create distal stop 184 and proximal stop 186, andovalized or flattened hypotube 188, which in turn is soldered tostainless steel hypotube 180 which overlies tube 188 for fitting withinthe RHV housing. The flattened tubes are provided to prevent rotation.Glue 192 is used to lock the hypotube 180 assembly in place inside thehousing. The locking assembly is slid over inner catheter body 194 andglued in place. A gap 196 is left distal of the hypotube 182 so thathypotube 182 can be pushed distally to cause deflection. Although thehandle has been shown without a screw assembly for locking axialmovement of the inner catheter, such an assembly can be added to theproximal handle, if desired.

In use, stainless steel hypotube 182 will be allowed to move proximallyand distally axially until stops 184 and 186 are reached. Rotation willbe restricted due to flattened region on hypotube 182 and ovalizedhypotube 188 through which it freely moves. This rotational controlconcept can be used on deflectable microcatheter designs with a fulllength guidewire lumen or deflectable microcatheters with rapid exchangeports. In general, this rotational control design can be used on anydesign that requires pure axial movement with little or no rotation. Inaddition, although this design uses flattened hypotubes, the concept canbe injection molded into parts such as rotation hemostasis valves (RHV)to quicken manufacturing.

FIG. 17 illustrates a coaxial bi-directional microcatheter 198 with arapid exchange port 200. The purpose of the rapid exchange port is toallow a guidewire to be placed through the side of the inner lumen ofthe catheter for tracking. The rapid exchange port may be placedanywhere proximal of the deflecting section (D) of the catheter. Theexact placement will depend on bending radius used for design. In someembodiments, the exchange port 200 may be 6 mm from the distal tipalthough other distances are also contemplated. Also, the length of therapid exchange port which can be cut on the inner catheter may be longerin some embodiments than the cut on the outer catheter to accommodatedeflection with guidewire in place. However, they can also be cut to thesame length or the outer catheter can be cut longer than the inner.Because the inner and outer catheters move relative to one another, therapid exchange ports must also be able to move relative to one anotherto accommodate deflection. If the guidewire or other device will not bedeflected, the rapid exchange port can be placed in deflection sectionD.

This embodiment allows for introduction of other devices through theproximal end of the device. Shown extending from RHV 202 by way ofexample is an electrohydraulic lithotripsy (EHL) device 204, as made byNorthgate Technologies, Inc. (Illinois). Other possible devices forinsertion may include biopsy probes, guidewires or laser fibers, forexample.

FIGS. 18A and 18B illustrates an alternate embodiment of the distal tipdeflection mechanism 206. The design allows the inner shaft withattached components to rotate and deflect 360 degrees with respect tothe outer catheter. This is achieved by not attaching the column to theouter catheter and thus the column does not extend and attach bothcatheters. A portion L1 of the outer catheter 208, the outer coil 210,and band 212 have been removed in FIG. 18A to show the internalconstruction. Column 214 is attached to distal band 216 and proximalband 218, as in previous designs; however, a section of the columncontinues proximally where it passes under band 220 which would be gluedin place inside outer catheter 208. Attached at the proximal end of thecolumn is stop 222. This configuration will allow the column to turnwith the inner catheter body and attached components when it is torqued.

FIG. 18B illustrates the distal tip deflection mechanism 206 with outercatheter 208, distal outer coil 210 and band 212 in place and in use.The inner catheter 224 can be rotated causing the column, which is nowpart of the inner catheter, to rotate which allows 360 degree deflectionbecause it can deflect in any plane. When the outer catheter 208 isadvanced or the inner catheter 224 retracted, the outer catheter 208will make contact with end 226 and further movement will cause the tipto deflect. If the outer catheter is pulled proximally or inner catheter224 is advanced, stop 222 contacts the outer catheter and continuedmovement will cause the catheter to deflect in opposite direction.(Movement of the inner catheter, back and forth, will also causedeflection).

In some embodiments, a balloon 232, such as an angioplasty balloon, canbe provided on the deflectable microcatheter distal portion. In theembodiment of FIG. 19A, the balloon 232 is mounted proximal ofdeflecting distal tip 230. In the embodiment of FIG. 19B, distal tipportion 234 of the deflectable microcatheter has balloon 236 mounteddistal of deflecting distal tip 238. Other possible options includemounting the balloon in the middle of the deflection zone or at the verydistal end, for example.

Note the dimensions and ranges provided herein are given by way example,it being understood that other dimensions and ranges for the componentsdescribed herein are also contemplated.

The deflection of the catheter of the present invention can besummarized as follows. Bi-directional deflection of the distal tip of acoaxial microcatheter can be broken down into two distinct motions:axial pull deflection and axial push deflection. Axial pull deflectioncan be modeled as an eccentrically loaded column while axial pushdeflection can be modeled as an eccentrically loaded beam.

With respect to axial pull deflection, when no lateral support tube ispresent on the distal end of the catheter, the rectangular nitinol wire(or alternate column member structure such as a rod discussed above) ismodeled as an unsupported eccentrically loaded column. This means thatwhen the inner catheter is moved axially proximally with a force P inthe proximal direction, the distal end of the column (rectangularnitinol wire) will want to move axially toward its proximal end,resulting in compression (buckling) of the nitinol wire. This is shownin FIG. 12A which illustrates movement of the column 140 in absence ofthe lateral support tube to explain the tip concept of the presentinvention. With the lateral support tube (e.g., coil) provided, when theinner catheter is pulled axially with a force P in the proximaldirection, the column (e.g., rectangular nitinol wire) will attempt tocompress (buckle) axially however it will be restricted by the lateralreinforcement (support), e.g., tube 50. Since the tip can no longer failaxially (in compression), it will fail laterally (deflect) (see FIGS.13A and 13C). It should be appreciated that axial proximal movement ofthe inner catheter is discussed. However, it should be appreciated thatdistal movement of the outer catheter would achieve the same effect.Therefore, as used herein, relative movement includes movement of theinner catheter with respect to the outer catheter, movement of the outercatheter with respect to the inner catheter, or movement of both inopposite directions with respect to each other.

With respect to axial push deflection, when no lateral support tube ispresent on the distal end of the catheter, the rectangular nitinol wire(or alternate column member structure such as a rod discussed above) ismodeled as an eccentrically loaded beam. This means that when the innershaft is pushed axially with a force P it will apply a moment to the endof the beam (e.g., rectangular nitinol wire), which causes it to bend.This is shown in FIG. 12B, with the lateral support tube (e.g., coil)provided and the inner catheter is pushed axially with a force P in thedistal direction, there will be a moment applied to the overall tipcausing it to bend (deflect) as shown in FIG. 13B and FIG. 13D. In thiscase, the addition of the coil does not change the action. It should beappreciated that axial distal movement of the inner catheter isdiscussed. However, it should be appreciated that proximal movement ofthe outer catheter would achieve the same effect. Therefore, as usedherein, relative movement includes movement of the inner catheter withrespect to the outer catheter, movement of the outer catheter withrespect to the inner catheter, or movement of both in oppositedirections with respect the each other.

Axial pushing and pulling can be considered in terms of an x-y axis.Axial pushing and pulling will happen on the x axis and bending(deflection) will end up at a point (x,y). So for compression of thecolumn, causing the tip to bend to y1 position, the distal end of thetip is traveling in the −x1 direction towards its proximal end (−x2).

Thus, as can be appreciated, in the coaxial catheter arrangement of thepresent invention, deflection of the distal tip is achieved by an axialmotion, rather than a pulling down on the distal tip as in prior artnon-coaxial catheters. Thus, the catheter itself is being used to bendthe distal tip as opposed to the prior art side by side wire andcatheter. Viewed in another way, the bending is achieved not by pullingin the direction of bending but by an axial movement. The structure ofthe deflectable catheter of the present invention saves space to reducethe overall size (diameter) of the catheter to provide a reduced profilefor insertion. It also provides space for fluid flow to enhancedeflection (by enhancing relative movement of the inner and outercatheters) without requiring an increase in the size (diameter) of thecatheter.

While the above description contains many specifics, those specificsshould not be construed as limitations on the scope of the disclosure,but merely as exemplifications of preferred embodiments thereof. Thoseskilled in the art will envision many other possible variations that arewithin the scope and spirit of the disclosure as defined by the claimsappended hereto.

What is claimed is:
 1. A bi-directional deflectable catheter comprising:an outer tubular member having a proximal end, a distal end and a firstlumen; an inner tubular member having a proximal end, a distal end and asecond lumen extending to the distal end, the inner member having a wallsurrounding the second lumen, the inner member positioned within thefirst lumen of the outer member, the inner member and outer member beingrelatively movable; and an elongated column member having a first endand a second end, the column member positioned external of the wall ofthe inner member and radially of the second lumen so the elongatedcolumn member is outside an outer diameter of the second lumen, thecolumn member fixed at a first end to the distal end of the inner memberand fixed at a second end to the distal end of the outer member, whereinthe elongated column member is configured to buckle in a region betweenthe first end and the second end upon relative movement of one or bothof the inner and outer members but is restrained from buckling andtherefore restrained from axial compression to effect lateral deflectionof a distal tip portion of the catheter, the distal tip portion of thecatheter being deflectable in first and second opposing directions froma longitudinal axis of the catheter.
 2. The catheter of claim 1, furthercomprising a reinforcement member positioned over the column member torestrain buckling and axial compression of the column member.
 3. Thecatheter of claim 1, wherein the column member is composed of a metaland the inner member is composed of a polymer.
 4. The catheter of claim1, wherein a cross-sectional dimension of a region of the column memberbetween the first and second ends extending external and adjacent aregion of the inner member is less than a cross-sectional dimension ofthe region of the inner member adjacent the column member.
 5. Thecatheter of claim 1, wherein the column member is in the form of one ofa wire or ribbon.
 6. The catheter of claim 1, further comprising amarker band at a region where the column member is fixed to the innermember.
 7. The catheter of claim 1, further comprising a marker band ata region where the column member is fixed to the outer member.
 8. Thecatheter of claim 1, wherein the column member extends inside a markerband overlying the inner member.
 9. The catheter of claim 1, wherein adistal tip portion is deflectable to an angle of 90 degrees with respectto the longitudinal axis.
 10. The catheter of claim 1, wherein the innermember includes a lubricious inner liner.
 11. A bi-directionaldeflectable catheter comprising: an outer tubular member having aproximal end, a distal end and a first lumen; an inner tubular memberhaving a proximal end, a distal end and a second lumen, the inner memberpositioned within the first lumen of the outer member, the inner memberand outer member being relatively movable; an elongated column memberextending distally along a length of a distal region of the innertubular member; and a movement restriction member positioned over thecolumn member to restrain buckling and axial compression of the columnmember; the column member configured to buckle and having a proximal endand a distal end, the column member being attached at a first end to thedistal end of the inner member and attached at a second end to thedistal end of the outer member, wherein a distal opening in the innertubular member fluidly communicating with the second lumen is distal ofthe second end of the column member attached to the outer member,wherein upon relative movement of one or both of the inner and outermembers the column member is restricted from buckling and thereforeaxial compression is restricted to effect lateral deflection of a distaltip portion of the catheter.
 12. The catheter of claim 11, wherein thecolumn member is composed of a metal and the inner member is composed ofa polymer.
 13. The catheter of claim 11, wherein a cross-sectionaldimension of a region of the column member between the first and secondends extending external and adjacent the distal region of the innermember is less than a cross-sectional dimension of the distal region ofthe inner member adjacent the column member.
 14. The catheter of claim11, further comprising a marker band at one or both of a region wherethe column member is attached to the inner member and a region where thecolumn member is attached to the outer member.
 15. A bi-directionaldeflectable catheter comprising: an outer tubular member having aproximal end, a distal end and a first lumen; an inner tubular memberhaving a proximal end and a distal end, the inner member positionedwithin the first lumen of the outer member, the inner member and outermember being relatively movable; an elongated column member having afirst end and a second end, the column member attached at the first endto the distal end of the inner member and attached at the second end tothe distal end of the outer member; a movement restriction memberpositioned over the column member; and a marker band at the distal endof the inner member adjacent a region of attachment of the first end ofthe column member to the inner member, the inner member and the outermember joined together with the marker band and the column memberextending into the marker band, a distal tip portion of the catheter isdeflectable in first and second opposing directions from a longitudinalaxis of the catheter.
 16. The bi-directional deflectable catheter ofclaim 15, wherein the inner member has a circular cross-section alongits length.
 17. The bi-directional deflectable catheter of claim 15,wherein upon relative movement of one or both of the inner and outermembers the elongated column member is restricted from buckling by themovement restriction member and therefore axial compression isrestricted to effect lateral deflection of the distal tip portion of thecatheter.
 18. The bi-directional deflectable catheter of claim 17,wherein the column member extends distally of a distalmost end of theouter member and the catheter has a central longitudinal axis and thecolumn member is radially offset with respect to the centrallongitudinal axis of the catheter.
 19. The bi-directional deflectablecatheter of claim 15, wherein the movement restriction member iscomposed of a metal coil and the column member is composed of a metal.20. The bi-directional catheter of claim 17, wherein the distal tipportion is capable of deflection to 180 degrees in the absence of themovement restriction member.